Endemic (Balkan) nephropathy is a type of chronic interstitial nephritis of unknown etiology, discovered in rural areas of Bulgaria, Rumania, and Yugoslavia in the 1950's. The search for causative agents has been largely unsuccessful, but a mycotoxin, ochratoxin A, has been suggested to be the disease determinant. Our goal is to determine whether ochratoxin A is associated with this disease, by measuring the concentration of an enzyme found in proximal tubules of kidneys. This enzyme is cytosolic P-enolpyruvate carboxykinase (PEPCK) and we have found that exposure of rats or swine to small (8 ug/kg body weight) or large (5000 ug/kg body weight) amounts of ochratoxin A for 1 day to 4 months reduces the activity of this enzyme up to 60-70%. We have measured other enzymes such as phosphate-dependent glutaminase, pyruvate carboxylase, and hexokinase, in rats and in single renal biopsies of swine, and find that none of these are affected. PEPCK activity is not reduced by mercury, citrinin, or gentamicin. Our primary aim is to determine if suspected cases of endemic nephropathy in humans are associated with exposure to ochratoxin A. This will be accomplished by measuring PEPCK activity and activity of other enzymes in renal tissue from autopsy or biopsy samples. Patients and autopsy samples will be taken from endemic and nonendemic areas of Yugoslavia. Medical history, tissue ochratoxin A concentration, and symptoms characteristic of endemic nephropathy such as glucosuria will be relied upon to identify the patient population. We will also measure PEPCK activity and renal ochratoxin A concentration in swine from identified endemic areas of Yugoslavia. The second aim is to optimize the use of the renal biopsy and measurement of PEPCK activity as a test of ochratoxin-A induced nephropathy. This will be done by preparing a mitochondrial PEPCK antibody to selectively precipitate the mitochondrial form of the enzyme, which may not be affected by the toxin. Finally we will determine whether measurement of PEPCK activity or concentration in urine can be used as a selective test to indicate the presence of this toxin. This would lead to a noninvasive method to test the hypothesis that the disease is associated with ochratoxin A. If the toxin can be linked to endemic nephropathy, steps will be undertaken to reduce the ingestion of food contaminated with the fungus.